It is known that in many industrial processes and notably in the field of chemical engineering, various exchanges and transfers are greatly improved by applying within reactors, systems capable of mixing or stirring the reacting material. In these reactors, one often resorts to stirrers with blades.
However, when the material which one desires to submit to stirring, comprises a significant portion of solid phases, these stirring means prove to be unsuitable, notably owing to hydrodynamic effects which remain limited in the vicinity of the stirrer and to the magnitude of the torque required for setting this solid phase into motion.
Mounting the reactor on a horizontal or tilted axis and providing rotation of the latter around this axis, were also proposed. Application of such devices however is unwieldy and therefore costly, and connecting them with external units is delicate. Moreover, they may be used with difficulty in the case of mixtures dealing with large amounts of material.
When the material to be mixed consists of various solid phases, it is known that notably due to gravity, the material is packed in the bottom of the reactor, so that the homogeneity of the solid phase is difficult to ensure and there follows generation of zones inside these reactors which develop, each at their own rate, finally producing differently transformed batches of material.
Moreover, it is known that during transformation of divided solids, the material frequently includes aggregates either existing initially or having formed gradually, either under the effect of chemical or biochemical reactions which release new substances, or because of the addition of a liquid phase directed to promote or cause the sought-after reactions.
Various systems applicable to the treatment of divided solid materials also comprising liquid or even gas phases, and including aggregates of materials, have been proposed.
Extracting the solid material from the reactor for example by means of devices with buckets, shovels, or worm-screws, and then turning up this material in order to fragment it by suitable means and then reload it into the reactor, were thus proposed.
So-called “counter-rotary” kneading devices which essentially consist of two coaxial mixing units, positioned in a vertical axis cylindrical reactor, i.e., a scraping unit positioned at the periphery of the reactor and a central unit consisting of three superimposed propellers, were also proposed, both of these units being provided with opposite directions of rotation so as to submit the material to be mixed to shear stress enabling the aggregates to be broken up. Such a device is however complex, so that it is unwieldy to manage both as regards investments and operation.